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Tribological Study of the SOCNTs@MoS2 Composite as a Lubricant Additive: Synergistic Effect

Song, Wei, Yan, Jincan, Ji, Hongbing
Industrial & engineering chemistry process design and development 2018 v.57 no.20 pp. 6878-6887
Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, additives, ambient temperature, carbon nanotubes, dibutyl phthalate, energy-dispersive X-ray analysis, friction, lubricants, microstructure, molybdenum disulfide, nitric acid, process design, scanning electron microscopy, sulfuric acid, synergism, transmission electron microscopy, vapors
Different layers of MoS₂ were grown on the surface of carbon nanotubes (CNTs) successfully with a facile and effective chemical vapor deposition method. The pristine CNTs (PCNTs) were pretreated with 5 mol L–¹ HNO₃, 10 mol L–¹ HNO₃, and mixed acid (sulfuric acid/nitric acid = 3:1) to obtain weakly oxidized CNTs (WOCNTs), moderately oxidized CNTs (MOCNTs), and strongly oxidized CNTs (SOCNTs). According to the results of SEM, EDS, TEM, Raman, XRD, and XPS, more layers of MoS₂ were grown on the surface of SOCNTs uniformly due to the abundant defects on its surface. The friction-reducing and antiwear performance of dibutyl phthalate (DBP) containing SOCNTs, MoS₂, SOCNTs/MoS₂ mixture, and SOCNTs@MoS₂ composite were investigated under 392 N and 1200 rpm at room temperature by four-ball tribotester. The DBP containing 0.02 wt % SOCNTs@MoS₂ composite exhibited the best tribological performance, and the friction coefficient and wear scar diameter (WSD) were reduced by 57.93% and 19.08%, respectively. The synergistic effect between SOCNTs and MoS₂ was further explored by comparing the lubricant mechanism of the different additives. A possible mechanism was proposed, and the SOCNTs@MoS₂ composite can be deposited on the rubbing surface due to the microstructure and translated into tribo-film which can protect the friction pair.